This invention relates generally to a boom structure and more particularly to a boom structure having telescoping sections which are guided relative to each other by rollers. More specifically, the instant invention relates to a means for causing the telescoping boom sections to move relative to each other by means of a hydraulic cylinder having one end thereof affixed to a boom cradle and the other end affixed to one of said boom sections, such that upon actuation of the hydraulic cylinder, the boom sections may be moved relative to each other. A cylinder support is affixed to the hydraulic cylinder in order to maintain the axial alignment of the barrel and rod of the hydraulic cylinder when the hydraulic cylinder is in an extended position and at all other times.
Boom structures having telescoping boom sections which are movable relative to each other by means of a hydraulic cylinder are well known as exemplified by U.S. Pat. No. 3,666,125 to Gano et al and U.S. Pat. No. 3,329,291 to Przybylski et al, both of which are specifically incorporated by reference herein. The above noted patents disclose a boom structure and hydraulic actuating cylinder arrangement employed by the Gradall Hydraulic Excavator manufactured by The Warner & Swasey Company, New Philadelphia, Ohio.
The prior art typically employs an outer boom section having a telescoping inner boom section slidably movable therein with the rod end of a hydraulic cylinder affixed to the outer boom and the barrel of the hydraulic cylinder affixed to the inner boom in order to provide a means for relative movement between the inner and outer booms. For instance, as more fully disclosed in U.S. Pat. No. 3,329,291, FIG. 3, the outer boom 72 has affixed thereto the rod member 93 of hydraulic cylinder 90 with the barrel 92 of the hydraulic cylinder affixed to the inner boom 71. The barrel 92 of the hydraulic cylinder is affixed to the inner boom 71 at a point toward the middle of the barrel 92 in order to reduce cylinder droop caused by excessively long unsupported portions of the hydraulic cylinder when in the extended position. Hydraulic fluid is provided to the cylinder 90 through manifold 100 into hollow rod member 93 and subsequently into the barrel 92 to effect movement of the rod relative to the barrel.
While this known boom cylinder arrangement has been generally satisfactory, it does present some disadvantages. Specifically, the use of a hydraulic cylinder employing a hollow rod in order to provide means for actuation requires additional expense in the fabrication of the hydraulic cylinder itself, and in addition requires the use of a manifold for porting the hydraulic fluid to and from the rotating hydraulic cylinder with the attendant expense, maintenance and wear problems associated with the use of a manifold. P The instant invention overcomes the disadvantages of the prior art by providing a boom cylinder structure employing a conventional hydraulic cylinder structure adapted to remain stationary relative to the boom carrier and therefore does not require a hollow rod or a manifold. A boom cylinder support is provided in order to eliminate the problems associated with an extended boom cylinder supported only at its ends.